Method and apparatus for rolled fingerprint capture

• US 20030091219A1
• Filed: 09/20/2002
• Published: 05/15/2003
• Est. Priority Date: 08/19/1999
• Status: Active Grant

• Current Assignee: HID Global Corporation (Assa Abloy AB)
• Original Assignee: Sonavation, Inc.
• Inventors: Martinez, Chris J., Scott, Walter Guy
• Granted Patent: US 7,095,880 B2
• Time in Patent Office: Days
• US Class Current: 382/124
• CPC Class Codes: G06V 40/1335 Combining adjacent partial images (e.g. slices) to create a composite input or reference pattern; Tracking a sweeping finger movement

Abstract

A method and apparatus for rolled fingerprint capture is described. The start of a fingerprint roll is detected. A plurality of fingerprint image frames are captured. A centroid window corresponding to each of the plurality of captured fingerprint image frames is determined. Pixels of each determined centroid window are knitted into a composite fingerprint image. The end of the fingerprint roll is detected.

Claims

1. A method for rolled fingerprint capture, comprising the steps of:

(1) detecting the start of a fingerprint roll;

(2) capturing a plurality of fingerprint image frames;

(3) determining a centroid window corresponding to each of the plurality of captured fingerprint image frames;

(4) knitting pixels of each determined centroid window into a composite fingerprint image; and

(5) detecting the end of said fingerprint roll.

2. The method of claim 1, wherein step (1) comprises the steps of:

(a) generating a pixel intensity difference count value between a current fingerprint image frame and a previous fingerprint image frame; and

(b) determining whether the generated pixel intensity difference count value is greater than a start roll sensitivity threshold value.

3. The method of claim 1, wherein step (1) comprises the steps of:

(a) generating a pixel intensity difference percentage value between a current fingerprint image frame and a previous fingerprint image frame; and

(b) determining whether the generated pixel intensity difference percentage value is greater than a start roll sensitivity threshold percentage value.

4. The method of claim 3, wherein step (a) comprises the steps of:

(i) capturing a current fingerprint image frame;

(ii) comparing the intensity of each pixel of the current fingerprint image frame to the intensity of a corresponding pixel of a previously captured fingerprint image frame to obtain a pixel intensity difference count value; and

(iii) calculating a pixel intensity difference percentage value.

5. The method of claim 4, wherein step (ii) comprises the step of:

finding compared pixels to be different if their intensity values differ by greater than a pixel intensity difference threshold.

6. The method of claim 1, wherein step (1) comprises the step of:

(a) displaying a panel;

(b) permitting a user to select a roll speed for setting a fingerprint image capturing area sampling interval;

(c) permitting a user to select a start sensitivity threshold value for detecting the start of the fingerprint roll;

(d) permitting a user to select a stop sensitivity threshold value for detecting the stop of the fingerprint roll;

(e) permitting a user to select a guided roll mode; and

(f) permitting a user to activate a roll mode.

7. The method of claim 1, wherein said step (3) comprises the steps of:

(a) generating a pixel window in a captured fingerprint image frame;

(b) finding a leading edge column and a trailing edge column of a fingerprint image in the corresponding generated pixel window; and

(c) generating the centroid window in the captured fingerprint image frame, wherein the centroid window is bounded by the leading edge column found and the trailing edge column found.

8. The method of claim 7, wherein said step (a) comprises the step of:

generating the pixel window in the captured fingerprint image frame that is centered in an axis perpendicular to the direction that a finger is rolled, the window including columns of a predetermined pixel number in the axis perpendicular to the direction that the finger is rolled, and the window having a length in an axis parallel to the direction that the finger is rolled equal to the number of pixels spanning the captured fingerprint image frame along that axis.

9. The method of claim 7, wherein step (b) comprises the steps of:

(i) building a histogram representative of the cumulative pixel intensity of pixels present in each column of the generated window;

(ii) scanning through the histogram in the direction opposite that in which the finger is rolled for a difference in the total pixel intensities of first adjacent columns of the generated pixel window that is greater than a first fingerprint edge threshold to find a leading edge; and

(iii) scanning through the histogram in the direction in which the finger is rolled for a difference in the total pixel intensities of second adjacent columns of the generated pixel window that is greater than a second fingerprint edge threshold to find a trailing edge.

10. The method of claim 9, further comprising the steps of:

(iv) selecting the column of darker total pixel intensity of the first adjacent columns as the leading edge column; and

(v) selecting the column of darker total pixel intensity of the second adjacent columns as the trailing edge column.

11. The method of claim 1, wherein step (iv) comprises the steps of:

(a) comparing the intensity of each pixel of the determined centroid window to the intensity of a corresponding pixel of a composite fingerprint image; and

(b) replacing the pixel of the composite fingerprint image with the corresponding pixel of the determined centroid window if the pixel of the determined centroid window is darker than the corresponding pixel of the composite fingerprint image.

12. The method of claim 1, wherein step (5) comprises the steps of:

(a) generating a pixel intensity difference count value between a current fingerprint image frame and a previous fingerprint image frame; and

(b) determining whether the generated pixel intensity difference count value is less than a stop roll sensitivity threshold value.

13. The method of claim 1, wherein step (5) comprises the steps of:

(a) generating a pixel intensity difference percentage value between a current fingerprint image frame and a previous fingerprint image frame; and

(b) determining whether the generated pixel intensity difference percentage value is less than a stop roll sensitivity threshold percentage value.

14. The method of claim 13, wherein step (a) comprises the steps of:

(i) capturing a current fingerprint image frame;

(ii) comparing the intensity of each pixel of the current fingerprint image frame to the intensity of a corresponding pixel of a previously captured fingerprint image frame to obtain a pixel intensity difference count value; and

(iii) calculating a pixel intensity difference percentage value.

15. The method of claim 14, wherein said comparing step comprises the step of:

finding compared pixels to be different if their intensity values differ by greater than a pixel intensity difference threshold.

16. The method of claim 1, wherein step (5) comprises the steps of:

(a) displaying a panel;

(b) permitting a user to save a composite fingerprint image; and

(c) permitting the user to exit the rolled fingerprint capture algorithm.

17. An apparatus for rolled fingerprint capture, comprising:

a fingerprint scanner;

a computer system coupled to said fingerprint scanner, wherein said computer system comprises a rolled fingerprint capture module; and

a display that displays a composite fingerprint image generated by said rolled fingerprint capture module, wherein said rolled fingerprint capture module determines a centroid window corresponding to each of a plurality of fingerprint image frames captured by said fingerprint scanner and knits pixels of each said determined centroid window into a composite fingerprint image.

18. The apparatus of claim 17, further comprising a communications interface signal coupled to said computer system.

19. The apparatus of claim 17, wherein said computer system comprises:

a centroid window determiner module.

20. The apparatus of claim 17, wherein said rolled fingerprint capture module comprises:

a pixel knitting module that compares the intensity of each pixel of said each determined centroid window to the intensity of a corresponding pixel of said composite fingerprint image and replaces said corresponding pixel of said composite fingerprint image with said pixel of said each determined centroid window if said pixel of said each determined centroid window is darker than said corresponding pixel of said composite fingerprint image.

21. The apparatus of claim 17, wherein said computer system comprises:

a fingerprint roll detector module.

22. The apparatus of claim 21, wherein said fingerprint roll detector module comprises:

a fingerprint roll start detector module; and

a fingerprint roll stop detector module.

23. The apparatus of claim 17, wherein said rolled fingerprint capture module comprises:

a fingerprint capture module;

a fingerprint image format module coupled to said fingerprint capture module; and

a fingerprint image display module coupled to said fingerprint image format module.

24. A system for rolled fingerprint capture, comprising:

a fingerprint roll start detector module that detects the start of a fingerprint roll in a fingerprint image capturing area;

a centroid window determiner module that determines a centroid window corresponding to each of a plurality of captured fingerprint image frames;

a pixel knitting module that knits pixels of said each determined centroid window into a composite fingerprint image; and

a fingerprint roll stop detector that detects the end of the fingerprint roll.

25. The system of claim 24, wherein said pixel knitting module knits pixels of each of said determined centroid window into said composite fingerprint image, wherein said pixel knitting module compares the intensity of each pixel of said each of said determined centroid window to the intensity of a corresponding pixel of said composite fingerprint image and replaces said corresponding pixel of said composite fingerprint image with said pixel of said each of said determined centroid window if said pixel of said each of said determined centroid window is darker than said corresponding pixel of said composite fingerprint image.

26. A system for rolled fingerprint capture, comprising:

means for detecting the start of a fingerprint roll;

means for capturing a plurality of fingerprint image frames;

means for determining a centroid window corresponding to each of the plurality of captured fingerprint image frames;

means for knitting pixels of each determined centroid window into a composite fingerprint image; and

means for detecting the end of said fingerprint roll.

27. A computer program product comprising a computer useable medium having computer program logic recorded thereon for enabling a processor in a computer system to permit a user to capture a rolled fingerprint, said computer program logic comprising:

means for enabling the processor to detect the start of a fingerprint roll;

means for enabling the processor to capture a plurality of fingerprint image frames;

means for enabling the processor to determine a centroid window corresponding to each of the plurality of captured fingerprint image frames;

means for enabling the processor to knit pixels of each determined centroid window into a composite fingerprint image; and

means for enabling the processor to detect the end of said fingerprint roll.